The invention relates to a method for cooling a metallurgical furnace having at least one cooling element which is flown through by a cooling medium. The invention further relates to a cooling circuit system for metallurgical furnaces, comprising at least one cooling element with a feed and a discharge for a cooling medium, a heat exchanger and a recirculation pump.
Water is usually used as a cooling medium in cooling elements in metallurgical furnaces. In prior art there are various designs of such cooling elements, which differ from each other in terms of geometry and guidance of the cooling medium. The cooling elements may be installed at the wall, in the wall or at the tap hole, with the ones in the furnace wall providing for the most intensive cooling.
For these very effective cooling elements in the furnace wall, there are available in general two embodiments, namely, one with water flow within the furnace shell, and the other one with water flow outside of the furnace shell. The cooling elements with water flow within the furnace shell are preferably used in flash smelters and electric furnaces as these provide for a great amount of heat transfer, without—as it is the case with the cooling elements with water flow outside of the furnace shell—a plurality of openings in the furnace shell being required.
The great disadvantage of the cooling elements with water flow in the furnace shell, however, is the cooling medium water itself. In the case of damage at the cooling element or a breaking of the cooling element, respectively, and the leakage of water associated therewith, water may enter the furnace.
Due to the reaction of water and molten metal and the hydrogen reactions associated therewith, there is given a high risk of explosion (oxyhydrogen reaction), in particular if the leakage is situated in the cooling element and, hence, the site of the water leakage is situated underneath the bath level. These explosions, due to the reaction with water, may lead to the destruction of the furnace.
Water entering the furnace may further lead to big problems with the refractories of the furnace lining if—as is common in the non-iron metal and ferro-alloy industry—MgO-containing material is used. Upon contact with water, the reaction of periclase (MgO) into brucite (Mg(OH)2) takes place, i.e., hydration, and an increase in volume associated therewith of up to 115%:MgO+H2O→Mg(OH)2 
The increase of volume due to this reaction leads to cracks and in the worst case to sand-like disintegration of the refractory material. Further, the increase of volume causes uncontrolled movement of the refractory lining, which may impair the furnace shell.
Another big problem may occur when the furnace is heated. In the course of this the water, i.e., the residual moisture, leaves the refractory bricks. In order to minimize the risk of hydration of the MgO-containing bricks, which tends to occur in a temperature range from about 40 to 180° C., this temperature range is passed as fast as possible.
Crucial, however, is the region in the vicinity of the cooling elements. Due to the temperature of the cooling water, the temperature of the water-cooled cooling elements is significantly lower (<100° C.) than that of the adjoining refractory bricks, so that this may lead to water condensing between refractories and cooling element. This, in turn, will result in hydration and damage in this area.